Tester

ABSTRACT

A tester including a source and measuring device and a TX port connected to the source and measuring device is configured to determine a source reflection coefficient using an extension circuit. The extension circuit includes a calibration device having a power sensor. The calibration device is configured to provide a plurality of different terminations at the TX port. The tester is configured to calibrate a source power of the source and measuring device using the determined source reflection coefficient and the power sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of copending International Application No. PCT/EP2013/073992, filed Nov. 15, 2013, which is incorporated herein by reference in its entirety.

Embodiments of the present invention relate to a tester. Further embodiments relate to a system comprising a tester and an extension circuit. Further embodiments relate to a method for calibrating a source power of a source and measuring device of a tester. Some embodiments relate to a vector based in-system power calibration.

BACKGROUND OF THE INVENTION

With the need of many RF (RF=radio frequency) ports in ATE (ATE=automatic test equipment) systems it becomes more and more challenging to keep the overall calibration time low or even reduce it. To get additional RF ports more switches are used in a fan out structure which degrades RF performance.

FIG. 1 shows a block diagram of a conventional power calibration setup 10. The conventional power calibration setup 10 consists of a main circuit 12, a connection circuit 14, an external circuit 16, RF ports 18 and a power sensor 20.

As indicated in FIG. 1, one conventional method of a power calibration at each port 18 is the measuring of the absolute power at each port 18 over frequency when it is terminated with the reference impedance of the system (Z0). The technique can achieve very accurate results but costs time and is only appropriate with small port counts.

As disclosed in the WO 2012/084028, another approach is to use the exclude circuit for the fan out structure and an integrated power sensor that measures the RF input power at the TX port and transforms it with the known path loss to all other ports. This concept reduces calibration time by factor X.

But this is only valid for a 50Ω system, which means a 50Ω load and a 50Ω source connected with a 50Ω connection circuit. In reality, the output match is not 50Ω, it is a complex impedance. In addition, the input match of the power sensor and the match of every other through path is not 50Ω due to series resistance of RF switches and signal routing with VIAs and connectors, just like the connection circuit is not a 50Ω system too. This leaves an unknown mismatch error (ripple) that directly impacts power accuracy, as will become clear from FIGS. 2a and 2 b.

FIG. 2a shows in a diagram 30 the insertion loss of a non 50Ω connection circuit with a 50Ω source and a 50Ω load (first curve 32), and the insertion loss of the non 50Ω connection circuit with a non 50Ω source and a non 50Ω load (second curve 34). Thereby, the ordinate denotes the insertion loss in dB, where the abscissa denotes the frequency in GHz.

FIG. 2b shows in a diagram 36 the resulting mismatch error of the non 50Ω connection circuit with the non 50Ω source and the non 50Ω load (third curve 38). Thereby the ordinate denotes the mismatch error in dB, where the abscissa denotes the frequency in GHz.

SUMMARY

According to an embodiment, a tester may have: a source and measuring device; and a TX port connected to the source and measuring device; wherein the tester is configured to determine a source reflection coefficient using an extension circuit, wherein the extension circuit includes a calibration device having a power sensor, and wherein the calibration device is configured to provide a plurality of different terminations at the TX port; and wherein the tester is configured to calibrate a source power of the source and measuring device using the determined source reflection coefficient and the power sensor.

According to another embodiment, a system may have: a tester which may have: a source and measuring device; and a TX port connected to the source and measuring device; wherein the tester is configured to determine a source reflection coefficient using an extension circuit, wherein the extension circuit includes a calibration device having a power sensor, and wherein the calibration device is configured to provide a plurality of different terminations at the TX port; and wherein the tester is configured to calibrate a source power of the source and measuring device using the determined source reflection coefficient and the power sensor; and an extension circuit including a calibration device having a power sensor; wherein the tester and the extension circuit are connected via the TX port, and wherein the calibration device is configured to provide a plurality of different terminations at the TX port.

According to another embodiment, a method for calibrating a source power of a source and measuring device of a tester including a TX port connected to the source and measuring device may have the steps of: determining a source reflection coefficient using an extension circuit, wherein the extension circuit includes a calibration device having a power sensor, and wherein the calibration device is configured to provide a plurality of different terminations at the TX port; and calibrating the source power of the source and measuring device using the determined source reflection coefficient and the power sensor of the calibration device.

A tester comprising a source and measuring device and a TX port connected to the source and measuring device is provided. The tester is configured to determine a source reflection coefficient using an extension circuit. The extension circuit comprises a calibration device having a power sensor. The calibration device is configured to provide a plurality of different terminations at the TX port. The tester is configured to calibrate a source power of the source and measuring device using the determined source reflection coefficient and the power sensor.

According to the concept of the present invention, the source power of the source and measuring device of the tester can be calibrated (e.g., after connecting the tester to an extension circuit, or each time the tester is connected to an extension circuit via the TX port) by determining (in a first step) the source reflection coefficient using the extension circuit which may be provide for this purpose a plurality of different terminations, such as, for example, open, load and short, and by using (in a second step) the determined source reflection coefficient and a power sensor of the extension circuit.

A system comprising a tester and an extension circuit is provided. The tester comprises a source and measuring device and a TX port connected to the source and measuring device. The tester and the extension circuit are connected via the TX port. The tester is configured to determine a source reflection coefficient using an extension circuit. The extension circuit comprises a calibration device having a power sensor. The calibration device is configured to provide a plurality of different terminations at the TX port. The tester is configured to calibrate a source power of the source and measuring device using the determined source reflection coefficient and the power sensor.

A method for calibrating a source power of a source and measuring device of a tester comprising a TX port connected to the source and measuring device is provided. The method comprises determining a source reflection coefficient using an extension circuit, wherein the extension circuit comprises a calibration device having a power sensor, and wherein the calibration device is configured to provide a plurality of different terminations at the TX port. Further, the method comprises calibrating the source power of the source and measuring device using the determined source reflection coefficient and the power sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be detailed subsequently referring to the appended drawings, in which:

FIG. 1 shows a block diagram of a conventional power calibration setup;

FIG. 2a shows in a diagram the insertion loss of a non 50Ω connection circuit with a 50Ω source and a 50Ω load, and the insertion loss of the non 50Ω connection circuit with a non 50Ω source and a non 50Ω load;

FIG. 2b shows in a diagram the resulting mismatch error of the non 50Ω connection circuit with the non 50Ω source and the non 50Ω load;

FIG. 3 shows a block diagram of a tester according to an embodiment of the present invention;

FIG. 4 shows a block diagram of a system comprising a tester and an extension circuit, according to an embodiment of the present invention;

FIG. 5a shows an illustrative view of the reflection coefficients and transmission coefficients which may be effective at the TX port in the first state of the extension circuit;

FIG. 5b shows an illustrative view of the reflection coefficients and transmission coefficients which may be effective at the TX port and the RX port in the second state of the extension circuit;

FIG. 5c shows an illustrative view of the reflection coefficients which may be effective at the TX port in the third state of the extension circuit; and

FIG. 6 shows a flow chart of a method for calibrating a source power of a source and measuring device of a tester, according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Equal or equivalent elements or elements with equal or equivalent functionality are denoted in the following description by equal or equivalent reference numerals.

In the following description, a plurality of details are set forth to provide a more thorough explanation of embodiments of the present invention. However, it will be apparent to those skilled in the art that embodiments of the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form rather than in detail in order to avoid obscuring embodiments of the present invention. In addition, features of different embodiments described hereinafter may be combined with each other, unless specifically noted otherwise.

FIG. 3 shows a block diagram of a tester 100 according to an embodiment of the present invention. The tester 100 comprises a source and measuring device 102 and a TX port 104 connected to the source and measuring device 102. The tester 100 is configured to determine a source reflection coefficient Γ_(source) using an extension circuit 120. The extension circuit 120 comprises a calibration device 122 having a power sensor 124. The calibration device 122 is configured to provide a plurality of different terminations at the TX port. The tester 100 is configured to calibrate a source power of the source and measuring device 102 using the determined source reflection coefficient Γ_(source) and the power sensor 124.

According to the concept of the present invention, the source power P_(source) of the source and measuring device 102 of the tester 100 can be calibrated (e.g., after connecting the tester 100 to an extension circuit 120, or each time the tester 100 is connected to an extension circuit 120 via the TX port) by determining (in a first step) the source reflection coefficient using the extension circuit 120 which may be provide for this purpose a plurality of different terminations, such as open, load and short, and by using (in a second step) the determined source reflection coefficient and a power sensor 124 of the extension circuit 120.

As shown in FIG. 4, the calibration device 122 can be connected to the TX port in order to provide the plurality of different terminations at the TX port.

Moreover, the tester 100 can be configured to derive a power value P₁ to P_(n) at a RF port 121 ₁ to 121 _(n) of the extension circuit 120 using known parameters of the extension circuit 120. The RF port 121 ₁ to 121 _(n) can be used to connect the extension circuit 120 to a DUT (DUT=device under test).

Note that the extension circuit 120 can comprise up to n RF ports 121 ₁ to 121 _(n), wherein n is a natural number greater than or equal to 1. (n≧1).

For example, the extension circuit 120 can comprise 1, 2, 3, 5, 10, 20, 30, 50, 100 or even more RF ports 121 ₁ to 121 _(n).

In some embodiments, the tester 100 can further comprise a receiver 104 and a RX port connected to the receiver 104.

Observe that the tester 100 can comprise a connection circuit 130 comprising flexible cables for connecting the tester 100 to the extension circuit 120.

For example, the source and measuring device 102 can be connected to the TX port via a flexible cable 132 of the connection circuit 130. Similarly, the receiver 104 can be connected to the RX port via a flexible cable 134 of the extension circuit 130.

Thereby, an arrangement, alignment or course of the flexible cables 132 and 134 may vary each time the tester 100 is connected to an extension circuit 120. Thus, a calibration of the source power P_(source) of the source and measuring device 102 may be performed each time the tester 100 is connected to an extension circuit 120. Similarly, the receiver 104 may also be calibrated each time the tester 100 is connected to an extension circuit 120.

As already mentioned, the calibration device 122 of the extension circuit 120 can be configured to provide a plurality of different terminations at the TX port. The plurality of different terminations may include, for example, load, short and open. Thereby, the load may be provided by the power sensor 124 of the calibration device, or in other words, the power sensor 124 of the calibration device 122 may be used as the load.

The known parameters of the extension circuit 120 may include reflection S parameters of the extension circuit 120 and/or transmission S parameters of the extension circuit 120.

For example, the reflection S parameters of the extension circuit 120 may include an actual reflection coefficient Γ_(load) _(_) _(a) of the load in the extension circuit 120 referenced to the port TX.

Further, the reflection S parameters of the extension circuit 120 may include an actual reflection coefficient Γ_(short) _(_) _(a) of the short in the extension circuit 120 referenced to the port TX.

Further, the reflection S parameters of the extension circuit 120 may include an actual reflection coefficient Γ_(open) _(_) _(a) of the open in the extension circuit 120 referenced to the port TX.

Further, the reflection S parameters of the extension circuit 120 may include an actual reflection coefficient S_(TXTX) of the TX port in the extension circuit 120 referenced to the port TX, when the path in the extension circuit 120 is set from the port TX to the port RX.

Further, the reflection S parameters of the extension circuit 120 may include an actual reflection coefficient S_(RXRX) of the RX port in the extension circuit 120 referenced to the port RX, when the path in the extension circuit 120 is set from the port TX to the port RX.

For example, the transmission S parameters of the extension circuit 120 may include an actual transmission coefficient S_(TXRX) of the path from the port RX to the port TX of the extension circuit 120.

Further, the transmission S parameters of the extension circuit 120 may include an actual transmission coefficient S_(RXTX) of the path from the port TX to the port RX of the extension circuit 120.

Note that the reflection S parameters Γ_(load) _(_) _(a), Γ_(short) _(_) _(a), Γ_(open) _(_) _(a), S_(TXTX), S_(RXRX) and the transmission S parameters S_(TXRX), S_(RXTX) of the extension circuit 120 may be obtained with a network analyzer before connecting the extension circuit 120 to the tester 100 (in order obtain the known parameters of the extension circuit 120).

The source and measuring device 102 of the tester 100 can be configured to measure a plurality of reflection coefficients at the TX port for the plurality of different terminations provided by the calibration device 122 at the TX port. Thereby, the tester 100 can be configured to determine the source reflection coefficient Γ_(source) based on the measured reflection coefficients.

For example, the tester 100 can be configured to control the calibration device 122 to provide the load at the TX port, and to measure the reflection coefficient of the load in the extension circuit 120 referenced to the port TX with the source and measuring device 102, in order to obtain a measured reflection coefficient Γ_(load) _(_) _(m) of the load.

Further, the tester 100 can be configured to control the calibration device 122 to provide the short at the TX port, and to measure the reflection coefficient of the short in the extension circuit 120 referenced to the port TX with the source and measuring device 102, in order to obtain a measured reflection coefficient Γ_(short) _(_) _(m) of the short.

Further, the tester 100 can be configured to control the calibration device 122 to provide the open at the TX port, and to measure the reflection coefficient of the open in the extension circuit 120 referenced to the port TX with the source and measuring device 102, in order to obtain a measured reflection coefficient Γ_(open) _(_) _(m) of the open.

As already indicated, the tester 100 can be configured to determine the source reflection coefficient Γ_(source) based on the measured reflection coefficients Γ_(load) _(_) _(m), Γ_(short) _(_) _(m), Γ_(open) _(_) _(m). Moreover, the tester 100 can be configured to determine the source reflection coefficient Γ_(source) further based on the known reflection coefficients Γ_(load) _(_) _(a), Γ_(short) _(_) _(a), Γ_(open) _(_) _(a) of the extension circuit 120 at the TX port.

In other words, the tester 100 can be configured to determine the source reflection coefficient Γ_(source) based on the measured reflection coefficients Γ_(load) _(_) _(m), Γ_(short) _(_) _(m), Γ_(open) _(_) _(m) and based on the known reflection coefficients Γ_(load) _(_) _(a), Γ_(short) _(_) _(a), Γ_(open) _(_) _(a) of the extension circuit 120 at the TX port.

Finally, the tester 100 can be configured to calibrate the source power P_(source) of the source and measuring device 102 by obtaining a measured source power P_(TX) at the port TX using the power sensor 124 of the extension circuit 120 and determining an actual source power P′_(source) available for a termination of the TX port with a reference impedance using the measured source power P_(TX) and the source reflection coefficient Γ_(source).

Thereby, the tester 100 can be configured to determine a calibration factor calfactor for calibrating the source power P_(source) based on the set source power P_(source) set at the source and measuring device and the actual source power P′_(source).

The above described principle for calibrating the source power P_(source) of the source and measuring device 102 will be explained in further detail making reference to FIG. 4.

Note that the tester 100 may also be configured to calibrate a receiver power P_(RX) of the receiver 104.

The tester 100 can be configured to control the extension circuit 120 to set up a loopback path connecting the TX port and the RX port via the extension circuit 120, and to calibrate the receiver power P_(RX) of the receiver 104 using the calibrated source power P_(source) and a power sensor 106 of the receiver 104.

Thereby, the tester 100 can be configured to determine a reflection coefficient Γ_(RX) presented by a receiver path 108 to the extension circuit 120 at the RX port by using a measured reflection coefficient Γ′_(RX) measured at the port TX with the source and measuring device 102 under the condition that the TX port is connected with the RX port and that the RX port is connected to the receiver path 108, and known parameters of the extension circuit 120, and to calibrate the receiver power P_(RX) further based on the determined reflection coefficient Γ_(RX) presented by the receiver path 108 to the extension circuit 120 at the RX port.

Further, the tester 100 can be configured to calibrate the receiver power P_(RX) by calculating a receiver power at the RX port using the determined reflection coefficient Γ_(RX) presented by the receiver path 108 to the extension circuit 120 at the RX port and known parameters of the extension circuit.

Finally, the tester 100 can be configured to derive a power input to the extension circuit 120 from a device under test on the basis of a power value measured by the receiver 104 of the tester 100.

For example, a device under test can be connected to at least one of the ports 121 ₁ to 121 _(n) of the extension circuit 120, wherein the tester 100 can be configured to derive a power P₁ to P_(n) input into the extension circuit 120 via at least one of the ports 121 ₁ to 121 _(n) on the basis of a power value measured by the receiver 104 of the tester 100.

The above described principle for calibrating the receiver power P_(RX) of the receiver 104 will also be explained in further detail making reference to FIG. 4.

Note that the following description, although referring to a system 140 comprising the tester 100 and the extension circuit 120, is also applicable to the tester 100, e.g., shown in FIG. 3.

FIG. 4 shows a block diagram of a system 140 comprising the tester 100 and the extension circuit 120, according to an embodiment of the present invention.

As shown in FIG. 4, the tester 100 and the extension circuit 120 can be connected via the TX port and the RX port. Moreover, the extension circuit 120 may be connected to a device under test via the RF ports P₁ to P_(n).

In contrast to FIG. 3, the extension circuit 120 (e.g., excluded circuit) further comprises a switch matrix 125 connected between the TX port, the RX port and at least one of the RF ports P₁ to P_(n).

In a first state, the extension circuit 120 can be configured to provide a loopback path by connecting the TX port and the RX port. For example, the extension circuit 120 can be controlled (e.g., by the tester 100) to provide the loopback path by connecting the TX port and the RX port via the switch matrix 125.

Note that FIG. 5a shows an illustrative view of the reflection coefficients Γ_(source), Γ_(RX), S_(TXTX) and S_(RXRX) and transmission coefficients S_(TXRX) and S_(RXTX) which may be effective at the TX port in the first state of the extension circuit 120.

In a second state, the extension circuit 120 can be configured to connect at least one of the RF ports 121 ₁ to 121 _(n) to the TX port and/or RX port. For example, the extension circuit 120 can be controlled (e.g., by the tester 100) to connect at least one of the RF ports 121 ₁ to 121 _(n) to the TX port and/or RX port via the switch matrix 125.

Note that FIG. 5b shows an illustrative view of the reflection coefficients Γ_(source), Γ_(RX), S_(TXTX) and S_(RXRX) and transmission coefficients S_(TXPn) and S_(PnRx) which may be effective at the TX port and the RX port in the second state of the extension circuit 120.

Further, the extension circuit 120 can compromise a switch 126 connected to the calibration device 122 and connected between the TX port and the switch matrix 125.

In the first state and in the second state, the extension circuit 120 can be configured to connect the TX port to the switch matrix 125, wherein in a third state the extension circuit 120 can be configured to connect the TX port to the calibration device 122.

Note that FIG. 5c shows an illustrative view of the reflection coefficients Γ_(load) _(_) _(a), Γ_(short) _(_) _(a), Γ_(open) _(_) _(a) and Γ_(source) which may be effective at the TX port in the third state of the extension circuit 120.

In the following, a possible calibration procedure (e.g., performed by the tester 100) of the source power P_(source) of the source and measuring device 102 and of the receiver power P_(RX) of the receiver 104 is described.

In other words, in the following, an integrated high accuracy power calibration technique between two RF circuit parts 100 and 120 with the usage of their characteristic impedances and the determining of the unknown output match of an TX/RX system with circuit integrated hardware only is described (apparatus for measuring linear and nonlinear port parameters (source and measuring device) 102 in the main circuit (tester) 100 and calibration standards such as open, short, load in the excluded circuit (extension circuit) 120).

Eliminating the in the introductory part mentioned mismatch uncertainty needs a vector based compensation knowing the output match Γ_(source) at the port TX and the input match Γ_(load) of the excluded circuit.

Solving equation (1) for a source power P_(source) gives the power P_(TX) at the port TX:

$\begin{matrix} {P_{TX} = {P_{source}^{\prime}\frac{1 - {\Gamma_{{load}\; \_ \; a}}^{2}}{{{1 - {\Gamma_{{load}\; \_ \; a}\Gamma_{source}}}}^{2}}}} & (1) \\ {P_{source}^{\prime} = {P_{source} + {calfactor}}} & (1.1) \end{matrix}$

Thereby, P_(TX) is the power at the port TX which is measured with the power sensor 124 of the extension circuit, P′_(source) is the actual power of the source and measuring device 102 when the TX port is loaded with the power sensor 124 of the extension circuit 120, and calfactor is the power difference between P′_(source) and P_(source).

The input match Γ_(load) _(_) _(a) can be measured after assembly as a part of the fabrication calibration, which also includes the power sensor calibration and the S parameter measurement of all paths.

Unknown is the output match of the main circuit 100 transformed through the connection circuit 130 at the point where the excluded circuit 120 is connected to (port TX). While calibrating the apparatus for measuring linear and nonlinear port parameters 102 of the main circuit 100, the forward source match (Γ_(source)) referenced to TX can be determined, too.

With three terminations (open, short, load (a matched power sensor 124)) the one port calibration at TX can be done.

All terminations are installed inside the excluded circuit 120 routed via a switch to the TX port.

The actual reflection coefficient Γ_(open) _(_) _(a) of the open in the extension circuit 120 referenced to the port TX is given by equation (2):

$\begin{matrix} {\Gamma_{{open}\_ a} = \frac{\Gamma_{{open}\_ m} - E_{df}}{{\Gamma_{source}\left( {\Gamma_{{open}\_ m} - E_{df}} \right)} + E_{rf}}} & (2) \end{matrix}$

The actual reflection coefficient Γ_(short) _(_) _(a) of the short in the extension circuit 120 referenced to the port TX is given by equation (3):

$\begin{matrix} {\Gamma_{{short}_{a}} = \frac{\Gamma_{{short}\_ m} - E_{df}}{{\Gamma_{source}\left( {\Gamma_{{short}\_ m} - E_{df}} \right)} + E_{rf}}} & (3) \end{matrix}$

The actual reflection coefficient Γ_(load) _(_) _(a) of the load in the extension circuit 120 referenced to the port TX is given by equation (4):

$\begin{matrix} {\Gamma_{{load}_{a}} = \frac{\Gamma_{{load}\_ m} - E_{df}}{{\Gamma_{source}\left( {\Gamma_{{load}\_ m} - E_{df}} \right)} + E_{rf}}} & (4) \end{matrix}$

Thereby, E_(df) is the forward directivity of the source and measuring device 102, and E_(rf) is the forward reflection tracking of the source and measuring device 102.

After measuring all three terminations Γ_(open) _(_) _(m), Γ_(load) _(_) _(m), and Γ_(short) _(_) _(m) a calculation yields all three terms for calibrating the Apparatus for measuring linear and nonlinear port parameters, including the source match of the circuit (Γ_(source)) at TX:

$\begin{matrix} {\Gamma_{source} = \frac{\begin{matrix} {{\Gamma_{{short}\_ a}\left( {\Gamma_{{load}\_ m} - \Gamma_{{open}\_ m}} \right)} +} \\ {{\Gamma_{{open}\_ a}\left( {\Gamma_{{short}\_ m} - \Gamma_{{load}\_ m}} \right)} -} \\ {\Gamma_{{load}\_ a}\left( {\Gamma_{{short}\_ m} - \Gamma_{{open}\_ m}} \right)} \end{matrix}}{\begin{matrix} {{\Gamma_{{short}\_ a}{\Gamma_{{load}\_ a}\left( {\Gamma_{{short}\_ m} - \Gamma_{{load}\_ m}} \right)}} +} \\ {{\Gamma_{l{oad}\_ a}{\Gamma_{{open}\_ a}\left( {\Gamma_{{load}\_ m} - \Gamma_{{open}\_ m}} \right)}} +} \\ {\Gamma_{{short}\_ a}{\Gamma_{{open}\_ a}\left( {\Gamma_{{open}\_ m} - \Gamma_{{short}\_ m}} \right)}} \end{matrix}}} & (5) \end{matrix}$

A power level P_(source) is set and the power sensor 124 in the excluded circuit 120 measures the power at the port TX. This value includes the calibration factor and the mismatch loss that appears when the path from port TX to the power sensor 124 is activated. The power P_(TX) which is available at a perfect 50 Ohm load can be calculated with equation (1).

To set the absolute power P_(n) at the port n (e.g., 50 Ohm terminated) equation (6) can be used:

$\begin{matrix} {P_{n} = {P_{source}\frac{{S_{nTX}}^{2}}{{{{S_{TXTX}\Gamma_{source}} - 1}}^{2}}}} & (6) \end{matrix}$

This technique also can be used for the power calibration of the receiver 104 of the main circuit 100.

Thereby, the match of the receiver 104 can be measured with the apparatus for measuring linear and nonlinear port parameters 102 through the TX/RX path (also possible for the connection TX to the port n (121 ₁ to 121 _(n))). Further, the power level P_(source) (P_(TX)) can be set (this is already known). Further, the power at the port RX can be calculated with equation (7):

$\begin{matrix} {P_{RX} = {P_{source}\frac{{S_{RXTX}}^{2}\left( {1 - {\Gamma_{RX}}^{2}} \right)}{{\begin{matrix} {{S_{TXTX}\Gamma_{source}} +} \\ {{\Gamma_{RX}\begin{pmatrix} {S_{RXRX} +} \\ {\Gamma_{source}\begin{pmatrix} {{S_{TXRX}S_{RXTX}} -} \\ {S_{TXTX}S_{RXRX}} \end{pmatrix}} \end{pmatrix}} - 1} \end{matrix}}^{2}}}} & (7) \\ {P_{RX} = {P_{n}\frac{{S_{RXn}}^{2}\left( {1 - {\Gamma_{RX}}^{2}} \right)}{{{{S_{RXRX}\Gamma_{RX}} - 1}}^{2}}}} & (8) \\ {\Gamma_{RX}^{\prime} = {S_{TXTX} + \frac{S_{TXRX}S_{RXTX}\Gamma_{RX}}{1 - {S_{RXRX}\Gamma_{RX}}}}} & (9) \end{matrix}$

This value can be compared to the measured power level, in order to calibrate the receiver 104.

Now, with the additional installed terminations inside the excluded circuit 120 a highly accurate power level compensation is possible for all ports of the excluded circuit 120 without using external equipment, such as a power sensor, source, calibration standards, etc.

This technique is timesaving, because the measurement for calibration is divided into two pieces.

First, all data which describes the excluded circuit 120 is measured after assembly. Second, the rest of the data that may be used for power calibration is reduced to a minimum, without user interaction.

With the vector based in-system power calibration the absolute power level can be very accurate calibrated for stimulus and receiver.

Subsequently, the steps, e.g., performed by the tester 100 (or system 140), for calibrating the source power P_(source) of the source and measuring device 102 and the receiver power P_(RX) of the receiver 104 are enumerated.

-   1. Assembly of excluded circuit 120. -   2. Measure/calibration of excluded circuit 120 (e.g., measuring     S-parameters of all paths and reflection coefficient of all     terminations with reference at TX (Γ_(load) _(_) _(a), Γ_(short)     _(_) _(a), Γ_(open) _(_) _(a)) and power sensor calibration     (referenced to TX).     -   As already mentioned above, unknown is the output match of the         main circuit 100 transformed through the connection circuit 130         at the point where the excluded circuit 120 is connected to         (port TX). While calibrating the apparatus for measuring linear         and nonlinear port parameters 102 of the main circuit 100, the         forward source match (Γ_(source)) referenced to TX can be         determined, too.     -   With three terminations (open, short, load (e.g., a matched         power sensor) the one port calibration at TX can be done.     -   All terminations are installed inside the excluded circuit 120         routed via a switch 126 to the TX port. -   3. Connect the excluded circuit 120 via the connection circuit 130     to the main circuit 100 (final position in testhead). -   4. Measure with apparatus for measuring linear and nonlinear port     parameters Γ_(load) _(_) _(m), Γ_(short) _(_) _(m), Γ_(open) _(_)     _(m) at port TX. -   5. Use equation (5) to calculate Γ_(source).     -   After measuring all three terminations Γ_(open) _(_) _(m),         Γ_(load) _(_) _(m) and Γ_(short) _(_) _(m) a calculation yields         all three terms for calibrating the apparatus for measuring         linear and nonlinear port parameters, including the source match         of the circuit (Γ_(source)) at TX. -   6. Set power P_(source) (at this point uncalibrated). -   7. Set path from TX to internal power sensor 124. -   8. Measure power P_(TX) at TX with power sensor 124 of excluded     circuit 120. -   9. With equation (1) calculate true P′_(source) (max power level at     TX is known (this level is the maximum power at TX if TX is     terminated with 50 Ohm and (almost) nothing is reflected from the     port back to the source)). -   10. Get calfactor=P′_(source)−P_(source) (this factor is only the     relation between the set power and the power, if TX is terminated     with 50 Ohm). -   11. Set path from TX to RX (loopback path)—this path is terminated     with Γ_(RX). -   12. Measure with the apparatus for measuring linear and non-linear     port parameters 102 the input match Γ′_(RX) of the port TX,     terminated with Γ_(RX). -   13. Calculate Γ_(RX) with equation (9). -   14. Set P_(source) (P′_(source)−calfactor). -   15. Calculate power P_(RX) at RX with equation (7). -   16. Measure power with sensor 106 on main circuit 100. -   17. This measured value represents the power P_(RX) at port     RX→receiver is abs. calibrated at RX. -   18. The receiver 104 has a(n) (almost) perfect linear     behavior→guaranteed per design, therefore one point is sufficient. -   19. All stimulus power levels can be measured with the calibrated     receiver 104 through the loopback path of the excluded circuit     120.→full stimulus calibration to the port TX. -   20. To set an accurate power level to the port n (device under test,     which has a 50 Ohm input impedance) a transformation from port TX to     port n may be used, with equation (6). -   21. To receive a signal a transformation from port n to port RX may     be used with equation (8).

FIG. 6 shows a method 200 for calibrating a source power P_(source) Of a source and measuring device 102 of a tester 100. The tester 100 comprises a TX port connected to the source and measuring device 102. The method 200 comprises a step 202 of determining a source reflection coefficient Γ_(source) using an extension circuit 120, wherein the extension circuit 120 comprises a calibration device 122 having a power sensor 124, and wherein the calibration device 122 is configured to provide a plurality of different terminations at the TX port. Further, the method 200 comprises a step 204 of calibrating the source power P_(source) of the source and measuring device 102 using the determined source reflection coefficient Γ_(source) and the power sensor 124.

Although some aspects have been described in the context of an apparatus, it is clear that these aspects also represent a description of the corresponding method, where a block or device corresponds to a method step or a feature of a method step. Analogously, aspects described in the context of a method step also represent a description of a corresponding block or item or feature of a corresponding apparatus. Some or all of the method steps may be executed by (or using) a hardware apparatus, like for example, a microprocessor, a programmable computer or an electronic circuit. In some embodiments, some one or more of the most important method steps may be executed by such an apparatus.

Depending on certain implementation requirements, embodiments of the invention can be implemented in hardware or in software. The implementation can be performed using a digital storage medium, for example a floppy disk, a DVD, a Blu-Ray, a CD, a ROM, a PROM, an EPROM, an EEPROM or a FLASH memory, having electronically readable control signals stored thereon, which cooperate (or are capable of cooperating) with a programmable computer system such that the respective method is performed. Therefore, the digital storage medium may be computer readable.

Some embodiments according to the invention comprise a data carrier having electronically readable control signals, which are capable of cooperating with a programmable computer system, such that one of the methods described herein is performed.

Generally, embodiments of the present invention can be implemented as a computer program product with a program code, the program code being operative for performing one of the methods when the computer program product runs on a computer. The program code may for example be stored on a machine readable carrier.

Other embodiments comprise the computer program for performing one of the methods described herein, stored on a machine readable carrier.

In other words, an embodiment of the inventive method is, therefore, a computer program having a program code for performing one of the methods described herein, when the computer program runs on a computer.

A further embodiment of the inventive methods is, therefore, a data carrier (or a digital storage medium, or a computer-readable medium) comprising, recorded thereon, the computer program for performing one of the methods described herein. The data carrier, the digital storage medium or the recorded medium are typically tangible and/or non-transitionary.

A further embodiment of the inventive method is, therefore, a data stream or a sequence of signals representing the computer program for performing one of the methods described herein. The data stream or the sequence of signals may for example be configured to be transferred via a data communication connection, for example via the Internet.

A further embodiment comprises a processing means, for example a computer, or a programmable logic device, configured to or adapted to perform one of the methods described herein.

A further embodiment comprises a computer having installed thereon the computer program for performing one of the methods described herein.

A further embodiment according to the invention comprises an apparatus or a system configured to transfer (for example, electronically or optically) a computer program for performing one of the methods described herein to a receiver. The receiver may, for example, be a computer, a mobile device, a memory device or the like. The apparatus or system may, for example, comprise a file server for transferring the computer program to the receiver.

In some embodiments, a programmable logic device (for example a field programmable gate array) may be used to perform some or all of the functionalities of the methods described herein. In some embodiments, a field programmable gate array may cooperate with a microprocessor in order to perform one of the methods described herein. Generally, the methods are advantageously performed by any hardware apparatus.

While this invention has been described in terms of several embodiments, there are alterations, permutations, and equivalents which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and compositions of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations and equivalents as fall within the true spirit and scope of the present invention.

Identifiers

-   P_(TX) power at the port TX, measured with the power sensor 124 of     the extension circuit 120. -   P_(RX) power at the port RX, measured with the power sensor 106 of     the receiver 104. -   P′_(source) actual power of the source and measuring device 102,     when the TX port is loaded with the power sensor 124 of the     extension circuit 120. -   P_(source) set power of the source and measuring device 102. -   Γ_(source) source match of the source and measuring device 102     referenced to the port TX. -   Γ_(RX) actual input math of the receiver 104 referenced to the port     RX. -   Γ′_(RX) input match of the receiver 104 measured with the source and     measuring device 102. -   P_(n) power at the port n (121 ₁ to 121 _(n)) of the extension     circuit 120. -   Γ_(load) _(_) _(a) actual reflection coefficient of the load in the     extension circuit 120 referenced to the port TX. -   Γ_(short) _(_) _(a) actual reflection coefficient of the short in     the extension circuit 120 referenced to the port TX. -   Γ_(open) _(_) _(a) actual reflection coefficient of the open in the     extension circuit 120 referenced to the port TX. -   Γ_(load) _(_) _(m) measured reflection coefficient of the load in     the extension circuit 120 referenced to the port TX with the source     and measuring device 102. -   Γ_(short) _(_) _(m) measured reflection coefficient of the short in     the extension circuit 120 referenced to the port TX with the source     and measuring device 102. -   Γ_(open) _(_) _(m) measured reflection coefficient of the open in     the extension circuit 120 referenced to the port TX with the source     and measuring device 102. -   S_(TXTX) actual reflection coefficient of the TX port in the     extension circuit 120 referenced to the port TX, when the path in     the extension circuit 120 is set from the port TX to the port RX. -   S_(RXRX) actual reflection coefficient of the RX port in the     extension circuit 120 referenced to the port RX, when the path in     the extension circuit 120 is set from the port TX to the port RX. -   S_(TXRX) actual transmission coefficient of the path from the port     RX to the port TX of the extension circuit 120. -   S_(RXTX) actual transmission coefficient of the path from the port     TX to the port RX of the extension circuit 120. -   E_(df) forward directivity of the source and measuring device 102. -   E_(rf) forward reflection tracking of the source and measuring     device 102. -   calfactor power difference between P′_(source) and P_(source). -   S_(nTX) actual transmission coefficient of the path from the port TX     to the port n (121 ₁ to 121 _(n)) of the extension circuit 120. -   S_(RXn) actual transmission coefficient of the path from the port n     (121 ₁ to 121 _(n)) to the port RX of the extension circuit 120. 

1. An apparatus, comprising: a tester configured to connect to an extension circuit and comprising: a source and measuring device including a source power; and a TX (transmission) port connected to the source and measuring device; wherein the tester is configured to determine a source reflection coefficient using the extension circuit, wherein the extension circuit comprises a calibration device comprising a power sensor; and wherein the tester is configured to calibrate the source power of the source and measuring device using the determined source reflection coefficient and the power sensor.
 2. The apparatus according to claim 1, wherein the tester is configured to derive a power value at a port of the extension circuit using known parameters of the extension circuit.
 3. The apparatus according to claim 2, wherein the known parameters of the extension circuit comprise at least one of: reflection S parameters of the extension circuit; and transmission S parameters of the extension circuit.
 4. The apparatus according to claim 1, wherein the calibration device is configured to provide a plurality of different terminations at the TX port, wherein the source and measuring device is configured to measure a plurality of reflection coefficients at the TX port for the plurality of different terminations provided by the calibration device at the TX port; and wherein the tester is configured to determine the source reflection coefficient based on the measured reflection coefficients.
 5. The apparatus according to claim 4, wherein the tester is configured to determine the source reflection coefficient further based on known reflection coefficients of the extension circuit at the TX port.
 6. The apparatus according to claim 1, wherein the calibration device is configured to provide a plurality of different terminations at the TX port, wherein the tester is configured to calibrate the source power of the source and measuring device by acquiring a measured source power at the port TX using the power sensor of the extension circuit, and determining an actual source power available for a termination of the TX port with a reference impedance using the measured source power and the source reflection coefficient.
 7. The apparatus according to claim 6, wherein the tester is configured to determine a calibration factor for calibrating the source power based on the set source power set at the source and measuring device and the actual source power.
 8. The apparatus according to claim 1, wherein the tester further comprises: a receiver including a receiver power and a power sensor; and a RX (receiving) port connected to the receiver; wherein the tester is configured to set up a loopback path connecting the TX port and the RX port via the extension circuit; and wherein the tester is configured to calibrate the receiver power of the receiver using the calibrated source power and the power sensor of the receiver.
 9. The apparatus according to claim 8, wherein the tester is configured to determine a reflection coefficient presented by a receiver path to the extension circuit at the RX port by using a measured reflection coefficient measured at the port TX with the source and measuring device under the condition that the TX port is connected with the RX port and that the RX port is connected to the receiver path, and known parameters of the extension circuit, and to calibrate the receiver power further based on the determined reflection coefficient presented by the receiver path to the extension circuit at the RX port.
 10. The apparatus according to claim 9, wherein the tester is configured to calibrate the receiver power by using a calculated receiver power at the RX port that is calculated by using the determined reflection coefficient presented by the receiver path to the extension circuit at the RX port and known parameters of the extension circuit.
 11. The apparatus according to claim 8, wherein the tester is configured to derive a power input to the extension circuit from a device under test on the basis of a power value measured by the receiver of the tester.
 12. A system, comprising: a tester comprising: a source and measuring device including a source power; and a TX (transmission) port connected to the source and measuring device; and an extension circuit comprising a calibration device comprising a power sensor; wherein the tester and the extension circuit are connected via the TX port, and wherein the calibration device is configured to provide a plurality of different terminations at the TX port; wherein the tester is configured to determine a source reflection coefficient using the extension circuit; and wherein the tester is configured to calibrate the source power of the source and measuring device using the determined source reflection coefficient and the power sensor.
 13. The system according to claim 12, wherein the tester further comprises a receiver and a RX (receiving) port connected to the receiver, wherein the tester and the extension circuit are connected via the RX port, and wherein the extension circuit is configured to provide a loopback path by connecting the TX port and the RX port.
 14. The system according to claim 12, wherein the tester further comprises a receiver and a RX (receiving) port connected to the receiver, wherein the extension circuit comprises at least one RF port configured to be connected to a device under test, and wherein the extension circuit is configured to connect the at least one RF port to the TX port and/or RX port.
 15. The system according to claim 12, wherein the tester further comprises a receiver and a RX (receiving) port connected to the receiver, wherein the tester and the extension circuit are connected via the RX port, wherein the extension circuit comprises a switch matrix connected between the TX port, the RX port and at least one RF port configured to be connected to a device under test; wherein in a first state the extension circuit is configured to provide a loopback path by connecting the TX port and the RX port; and wherein in a second state the extension circuit is configured to connect the at least one RF port to the TX port and/or RX port.
 16. The system according to claim 15, wherein the extension circuit comprises a switch connected to the calibration device and connected between the TX port and the switch matrix; wherein in the first state and the second state the extension circuit is configured to connect the TX port to the switch matrix; and wherein in a third state the extension circuit is configured to connect the TX port to the calibration device.
 17. The system according to claim 12, wherein the tester further comprises a connection circuit including flexible cables, wherein the tester is connected to the extension circuit via the flexible cables.
 18. A method of calibrating a source power of a source and measuring device of a tester, the method comprising: determining a source reflection coefficient using an extension circuit, wherein the tester includes a TX (transmission) port connected to the source and measuring device, wherein the extension circuit comprises a calibration device comprising a power sensor, and wherein the calibration device is configured to provide a plurality of different terminations at the TX port; and calibrating the source power of the source and measuring device using the determined source reflection coefficient and the power sensor of the calibration device.
 19. The method according to claim 18, wherein the tester and the extension circuit are connected via the TX port, wherein the method further comprises: determining reflection S parameters and transmission S parameters of the extension circuit with a network analyzer before connecting the extension circuit to the tester to acquire known parameters of the extension circuit. 